Martin
Looking at those graphs it seems to me possible to hypothesise that
if the later years are the start of a trend, then the Little
Corellas are gaining while Sulphur-cresteds are declining,
relatively. I suppose that one of the variables is how much the
Little Corellas and Sulphur-cresteds are recruiting from outside.
What the graphs do show is what a wonderful resource long-term data
collection by way of the GBS is.
Con
On 1/04/2012 9:39 AM, martin butterfield wrote:
Con
I think the answer is probably not. The attached GBS based graph
shows that the Corellas have - as you indicate - made a massive
increase in the recent past, but while the Cockies have a slight
downward trend from a high point, they are still a long way in
front. The graph also served to jog my mind about how far Cockies
have increased in the past 30 years.
In Ian Fraser's latest book he wonders if Corellas will overtake
Galahs (the latter having themselves only arrived in this area in
the last ~60 years).
Martin
On Sun, Apr 1, 2012 at 9:00 AM, Con Boekel <m("boekel.com.au","con");">>
wrote:
This morning a flock of 170 Little Corellas flew
over Haig Park in Turner. It is obvious that Little Corella
numbers in Canberra have climbed over the past quarter of a
century - certainly in the Inner North. I often notice Little
Corellas feeding in the same trees as Sulphur-crested
Cockatoos - on the same food.
The question I have is this - are our Sulphur-crested
Cockatoos declining as the Little Corellas increase?
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